Why Were the Southern Tornadoes So Deadly?

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Tornado-related deaths have declined dramatically over the past
few decades due to improved forecasts and better warnings, but
the massive outbreak on April 27 reported killed 318 people
across the Deep South. What happened?

The bottom line: Massive tornadoes hit populated cities head-on.
Forecasters had warned of an "insane" storm system for days, so
it's unlikely that the tornadoes caught many by surprise. But
with few basements in
Dixie Alley, not many places were safe in the paths of
tornadoes that had nearly 200-mph (322-kph) winds. Even solidly
built houses were swept away. Many entire neighborhoods were
completely obliterated. [ The
Tornado Damage Scale in Images ]

"The truth is, even if you did everything you were supposed to
do, unless you were in an underground bunker, you weren't going
to survive," James Spann of the ABC affiliate in Birmingham,
Ala., told the New York Times.

Vicious twisters

On Wednesday, more than 150 tornadoes were reported in the
southeastern United States. Bob Henson, a meteorologist with the
National Center for Atmospheric Research in Boulder, Colo., said
he "wouldn't at all be surprised," to see some of those storms
rated as EF-5, the highest rating on the Enhanced Fujita Damage
scale, with winds faster than 200 mph.

"Any tornado going through the heart of the city like that is
going to cause major damage," Henson told OurAmazingPlanet.

Historic outbreak

The latest outbreak wasn't just a few tornadoes in a few small
towns. Preliminary reports suggest that this outbreak could be
among the biggest of all time. Tornadoes roared on the ground for
hours and traveled miles between cities. One twister may have
traveled the 60 miles (97 kilometers) from Tuscaloosa, Ala., to
Birmingham.

"It looks like it was a very long-track tornado and those don't
happen that often," Henson said.

That tornado could be responsible for most of Alabama's 228
reported fatalities. When the damage assessments are finished,
the deadly outbreak will likely be the deadliest since 1974, when
308 were killed. The
deadliest outbreak of all time is believed to be the
Tri-State Tornado of March 18, 1925, which killed 695 people in
Missouri, Illinois and Indiana.

Those massive death tolls are rare today. Tornado-related deaths
have plummeted as forecasts and warnings have become more
precise. The 2000 to 2009 average for annual tornado-related
fatalities is 62, according to the National Climatic Data Center.

Deadly Dixie

Dixie Alley, the focus of this year's tornado season, is
notoriously deadly. Even a small tornado there can be deadly.

Unlike the flat, grass-covered plains of Tornado Alley, tornadoes
are hard to see in Dixie Alley. Trees and hilly terrain obscure
funnel clouds, a problem made even worse by the region's high
rate of nighttime tornadoes, which can hit when people are
sleeping.

To make matters worse, Dixie Alley is home to many manufactured
houses and mobile homes that have weak walls and poor -- or
nonexistent -- foundations. Before the April 27 outbreak, more
than half of this year's tornado-related deaths had occurred in
mobile homes.

Storm surveys are still ongoing, but it's likely that mobile home
deaths were common during the most recent tornado outbreak as
well.